1. Field of the Invention
The present invention is directed to a element for mattresses, made of resin.
2. Description of the Related Art
A conventional resin cushioning element of the type is disclosed in, for example, U.S. Pat. No. 5,588,165. This resin cushioning element is formed of plastic and forms axially-oriented through chambers having ribs. When a load is applied on a top of the conventional resin cushioning element, the cushioning element deforms similar to a wire coil spring.
However, the foregoing conventional resin cushioning element has the inner ribs, so an inner structure of a cavity of a mold assembly becomes complex.
U.S. Pat. No. 5,787,533 also discloses another conventional resin cushioning element. However, this is similar to the foregoing conventional resin cushioning element in structure. Thus, complexity of the mold assembly is still a problem.
Accordingly, a need exists for a resin cushioning element without the foregoing drawback.
The present invention has been developed to satisfy the need noted above and thus has a primary object of providing a resin cushioning element which is of one-piece construction comprising upstanding and downstanding portions alternately arranged in a regular manner to form a matrix having four peripheral surfaces.